Experimental and numerical Study on accumulation of plastic strain of SS316L cantilevered cylindrical shells under cyclic bending and combined (bending-torsion) loads

In this research, accumulation of plastic strain and softening behavior of stainless steel SS316L cylindrical shell under cyclic bending and combined loads (bending-torsion) are studied. Cyclic bending was under force-control and displacement-control but Combined loading was under displacement-control. Experimental tests were performed using an INSTRON 8802 servo-hydraulic machine. Under force-control loading with non-zero mean force, plastic strain was accumulated in continuous cycles that it was called ratcheting. Based on experimental results, linear relation was observed between plastic energy and rate of plastic deformation that shows the rigidity of fixtures using in experimental tests. Under displacement-control loading, softening behavior was observed due to growth of ovalization and the rate of softening became higher by using of the higher displacement amplitude. The crack growth up to failure is oblique in combined load due to torsion and bending loads whereas the crack growth is peripheral in bending load. The numerical analysis was carried out by ABAQUS software and nonlinear isotropic/kinematic hardening was compared with isotropic hardening and observed the nonlinear isotropic /kinematic hardening model simulates the softening behavior and accumulation of plastic strain of cylindrical shells under cyclic bending accurately.